$list: red orange yellow green grey blue pink;
$len:length($list: $list);
$width:percentage(1/$len);

@for $i from 1 through $len {

    .test .color#{$i} {
        width: $width;
        background-color: nth($list: $list, $n: $i);
        height: 10px;
        float: left;
    }
}
.test{
    width: 100%;
}